The present invention relates to a contact material for use in treatment of sewage, particularly in treatment of sewage by contact aeration method, and more in detail, relates to the contact material comprising a braid which is made of synthetic fibers and has loop piles, the weight of the synthetic fibers forming the loop pile part being from 40 to 90% by weight of the total amount of the synthetic fibers of the whole body of the braid.
In recent years, with the spread of sewage-treatment by the contact aeration method, various contact materials have been proposed.
Hitherto, as the contact material for treating sewages, several braid-like bodies have been known, such as a braid-like body made by winding a belt-like body, with a state of having ring-like or hook-like small bodies grown thickly thereon, round a core material comprising a metal such as aluminum and another braid-like body made by twisting the above-mentioned belt-like body to left or right and further one more braid-like body made by applying a tension to the vertical direction of the above-mentioned belt-like body.
However, there are several problems to utilize these contact materials as follows:
(1) it is complicate and expensive to construct the materials, PA0 (2) it is difficult to make micro-organisms adhere to the material in an amount sufficient to purify sewage because the thickness of braid-like bodies of the materials is limited due to the manufacturing process. (It has been observed that one adhered micro-organisms is detached from the materials), and PA0 (3) accordingly, the capacity to treat sewage becomes low or it becomes necessary to use large number of the materials to keep sewage clean.
As a result of the present inventors' studies on the contact material to which a sufficient amount of microorganism for effective cleaning of sewage adheres in a stabilized stage, with an intention of solving the above problems, it has been found that a contact material comprising a braid which is made of synthetic fibers and has loop piles thereon, the weight of the synthetic fibers of loop pile part being from 40 to 90% by weight of the synthetic fibers of the whole body of the braid, is able to achieve the cleaning of sewage in a smaller amount as compared to the conventional contact material, and based on this finding, the present invention has been attained.